AviationWeather Domestic SIGMET

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://api-evangelist.github.io/aviationweather/json-schema/aviationweather-airsigmet-schema.json",
  "title": "AviationWeather Domestic SIGMET",
  "description": "Decoded domestic SIGMET as returned by GET /api/data/airsigmet?format=json.",
  "type": "object",
  "properties": {
    "airSigmetId":   { "type": "integer", "description": "Internal AWC identifier." },
    "icaoId":        { "type": "string", "description": "Issuing center ICAO (typically KKCI for AWC)." },
    "receiptTime":   { "type": "string" },
    "validTimeFrom": { "type": "integer", "description": "UNIX epoch start." },
    "validTimeTo":   { "type": "integer", "description": "UNIX epoch end." },
    "alphaChar":     { "type": ["string","null"], "description": "Alpha designator (A-Z) for the SIGMET series." },
    "hazard":        { "type": "string", "enum": ["CONV","TURB","ICE","IFR","MTN_OBSC","ASH","TC","DS","SS"], "description": "Hazard type." },
    "severity":      { "type": ["string","null"], "description": "Severity (e.g. MOD, SEV)." },
    "rawAirSigmet":  { "type": "string", "description": "Raw SIGMET text." },
    "altitudeHi1":   { "type": ["integer","null"], "description": "Top altitude (feet)." },
    "altitudeLow1":  { "type": ["integer","null"], "description": "Base altitude (feet)." },
    "movementDir":   { "type": ["integer","null"], "description": "Movement direction (degrees true)." },
    "movementSpd":   { "type": ["integer","null"], "description": "Movement speed (knots)." },
    "geometry":      { "type": ["string","null"], "description": "Geometry as WKT polygon." }
  }
}